Still waiting for a reply from Marriott, but this is a little odd:

1. In the text they state this: "From November 5, 2007 – December 15, 2007, redeem your Marriott Rewards® points for American Airlines AAdvantage® miles and earn a 10% bonus for conversions!", which clearly seems to indicate they are encouraging you to take some of your MR points and convert them to AA miles.

2. In the T&C's, they say this: "To qualify to earn bonus miles under this promotion, you must be a Marriott Rewards member and choose to earn American Airlines AAdvantage miles in your Marriott Rewards member profile.", which seems to indicate that the promotion only applies to those who select miles instead of points for their earning preference. So, if you stay at a Farifield, for example, you get 1 mile/$ normally, and now you'd get 1.1 miles/$. Hardly exciting.